Commit a6b25da5 authored Feb 26, 2018 by Niklas Cassel Committed by David S. Miller Feb 27, 2018

net: stmmac: ensure that the device has released ownership before reading data



According to Documentation/memory-barriers.txt, we need to use a
dma_rmb() after reading the status/own bit, to ensure that all
descriptor fields are read after reading the own bit.

This way, we ensure that the DMA engine is done with the DMA
descriptor before we read the other descriptor fields, e.g. reading
the tx hardware timestamp (if PTP is enabled).

Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 95eb930a

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -1844,6 +1844,11 @@ static void stmmac_tx_clean(struct stmmac_priv *priv, u32 queue)
		if (unlikely(status & tx_dma_own))
		break;

		/* Make sure descriptor fields are read after reading
		* the own bit.
		*/
		dma_rmb();

		/* Just consider the last segment and ...*/
		if (likely(!(status & tx_not_ls))) {
		/* ... verify the status error condition */